Anionic surfactants such as alkyl ethoxy sulfates with short ethylene oxide chains, alkyl sulfates, alkyl benzene sulfonates, a-olefin sulfonates, and alkyl ethoxy carboxylates are known to be very effective for hard surface cleaning, but are also known to have more or less unfavorable "slippery" feel in use. This undesirable attribute is a problem to hard surface cleaning compositions, especially for dishwashing purposes.
There is therefore a considerable demand for a hard surface detergent composition which has good detergency and good storage stability while having good solution feel when cleaning and rinsing, particularly for dishwashing purposes. As defined herein, good solution feel is best defined as the absence of "slippery" or "slimy" feel, or a "draggy" kind of feel which one feels when the composition is in use. "Good solution feel" is an important attribute for commercial liquid detergent products. Those wash solutions which have good solution feel on hands and objects to be cleaned allow easy handling of the objects, and provide good rinsing characters. Such benefits are most appreciated for dishwashing purposes.
Many attempts have been made to improve solution feel using various technology. These attempts are usually directed towards the use of nonionic-type surfactants, and other suds enhancing-type and solvent-type components. Generally, these compositions have sacrificed detergency to obtain the improved solution feel.
Kokoku 46-43550 (Kao Corporation) teaches a liquid detergent composition which is mild to skin and has good detergency comprising alkaline earth metal salts of certain alkyl alkylene-oxy sulfate and certain alkyl alkylene-oxy carboxylates.
Kokai 51-125405 (The Procter & Gamble Company) teaches compositions comprising calcium and magnesium salts of anionic surfactants including alkyl ether sulfates and amine oxides, C.sub.1-5 alkanols and water, wherein the weight ratio of amine oxide to anionic surfactant is 1:100 to 1:2. Up to about 25% of the anionic surfactants can be monovalent salts.
U.S. Pat. No. 2,766,212 (General Aniline and Film Corporation) teaches compositions which comprise alkyl ether alkoxy sulfate salts and water soluble polyvalent salts of magnesium, calcium, iron, or aluminum of 5-50% by weight of the surfactant. Examples show compositions comprising at least 70% of the anionic surfactant in which magnesium and calcium ions help detergency.
U.S. Pat. No. 4,681,704 (The Procter & Gamble Company) teaches a detergent composition with effective grease removal comprising 10-50% alkaline earth metal salt, preferably magnesium, of anionic surfactants, 0.5-10% amine oxides, and 0.5-15% betaines.
However, the above mentioned disclosures use alkaline earth metals mainly for their cleaning benefits, and do not disclose or suggest the improvement to solution feel benefits contributed by calcium ions. Further, the compositions of the above mentioned disclosures have high divalent ion levels, so that they would be unstable upon storage in the context of the present invention, namely, would form undesirable precipitates of calcium. Preferred compositions and examples shown in the above disclosures also have high surfactant levels, and thus the amount of calcium needed to reduce or eliminate the "slippery feel" of the composition would place the composition into a phase where calcium is believed to easily precipitate.
Here, it has been found that by using calcium ions at a certain low level, a composition which provides improved solution feel without deteriorating storage stability is obtained.